基于压缩感知和熵计算的关键帧提取算法

针对关键帧提取问题,提出了一种基于压缩感知理 论和熵计算的关键帧提取算法, 首先通过构造符合有限等距性质要求的稀疏随机投影矩阵,将高维多尺度帧图像特征变换为 低维多尺度帧图像特征, 并形成视频镜头低维多尺度特征列向量组;然后通过随机权值向量与低维多尺度特征向量的 阿达玛乘积运算生成各 帧图像的匹配特征,并根据匹配特征的相似性度量完成镜头内部的子镜头分割;最后通过交 叉熵计算在每个子镜头 中得到可能的关键帧,并由图像熵计算确定最终的关键帧。实验表明,与传统方法相比,本 文算法提取的关键帧能够更精确、更稳定描述视频镜头内容。     

分布视频编码中基于帧间相关性的自适应关键帧选取算法

针对分布式视频编码(DVC)系统中固定周期关键帧选取(PKFS)方法忽视了帧间相关性的缺陷,提出了一种自适应关键帧选取(AKFS)算法。利用图像特征点检测与匹配的方法,将相邻图像的非匹配点作为帧间相关性的近似,把累积或平均非匹配点数超过阈值的帧判定为关键帧。在此基础上,提出改进的帧内插方案,以适应不同长度序列组的边信息生成;将零运动强度的关联帧合并为一帧图像参与编解码,进一步提高了系统的压缩效率。实验结果表明,对于不同运动特性的序列,本文提出的算法可以明显提升边信息帧的重建质量,使系统的率失真性能提高0.9～2.0 dB,并有效降低了编码传输码率。     

基于聚类的视频镜头分割和关键帧提取

镜头分割是基于内容的视频检索和浏览首先要解决的关键技术。视频分割为镜头后,下一步的工作就是进行关键帧提取,用以描述镜头的主要内容。提出了一种改进的基于聚类的镜头分割和关键帧提取算法．在无监督聚类中引入一个参考变量,解决了利用无监督聚类进行镜头分割和关键帧提取时可能产生的帧序不连续或分割错误的问题。在关键帧提取阶段,将镜头分割为子镜头后,引入图像熵的概念提取关键帧。实验结果表明了改进算法在镜头分割和关键帧提取方面的有效性。     

探讨基于Tsallis熵的视频关键帧提取技术

关键帧是视频中的一组有限数量的帧的子集,一个视频的关键帧序列能够合理地概括该视频信息,从而减少过大的视频数据对生产生活带来的承载负重.本文讨论了基于Tsallis熵的Jensen距离公式——JTD在视频关键帧提取中的应用.根据得到的差异性距离值JTD,首先检查子镜头边界,进而从每个子镜头中抽取一帧作为该镜头的代表帧,最终得到该段视频的关键帧序列.     

基于吞噬聚类的关键帧提取新算法

为了有效、自适应地提取镜头中的关键帧,提出了一种基于吞噬聚类的关键帧提取新算法。该算法通过邻近吞噬体的互相吞噬,聚类相似的数据对象,最后所剩吞噬体的吞噬中心即为视频帧的聚类中心,距离聚类中心最近的特征向量所代表的视频帧就是所需要的镜头关键帧。对该算法利用MATLAB仿真并通过与传统算法对比,结果表明,相对于传统算法,该算法的查全率和查准率都有了一定程度的提高。     

Sentiment-based sub-event segmentation and key photo selection

The number of people collecting photos has surged owing to social media and cloud services in recent years. A typical approach to summarize a photo collection is dividing it into events and selecting key photos from each event. Despite the fact that a certain event comprises several sub-events, few studies have proposed sub-event segmentation. We propose the sentiment analysis-based photo summarization (SAPS) method, which automatically summarizes personal photo collections by utilizing metadata and visual sentiment features. For this purpose, we first cluster events using metadata of photos and then calculate the novelty scores to determine the sub-event boundaries. Next, we summarize the photo collections using a ranking algorithm that measures sentiment, emotion, and aesthetics. We evaluate the proposed method by applying it to the photo collections of six participants consisting of 5,480 photos in total. We observe that our sub-event segmentation based on sentiment features outperforms the existing baseline methods. Furthermore, the proposed method is also more effective in finding sub-event boundaries and key photos, because it focuses on detailed sentiment features instead of general content features.     

基于网络的教学互动平台建设探索

建设教学互动平台,引出研究教学互动平台的理论基础及应用模型,从学习支持、互动学习、教师预约、在线答疑、交流共享、学习效果评价、学科建设等方面分析该平台应用于教学的效果和优势.平台提升了课程群的知识体系、培养学生的实践能力和创新精神.     

Video key frame extraction through dynamic Delaunay clustering with a structural constraint

Key frame based video summarization has emerged as an important area of research for the multimedia community. Video key frames enable an user to access any video in a friendly and meaningful way. In this paper, we propose an automated method of video key frame extraction using dynamic Delaunay graph clustering via an iterative edge pruning strategy. A structural constraint in form of a lower limit on the deviation ratio of the graph vertices further improves the video summary. We also employ an information-theoretic pre-sampling where significant valleys in the mutual information profile of the successive frames in a video are used to capture more informative frames. Various video key frame visualization techniques for efficient video browsing and navigation purposes are incorporated. A comprehensive evaluation on 100 videos from the Open Video and YouTube databases using both objective and subjective measures demonstrate the superiority of our key frame extraction method.     

高速SDH帧同步系统性能与同步码组选择

介绍了高速 SDH系统中的帧同步器的设计 ,分析了影响帧同步器性能的参数选择。在分析的基础上 ,以 STM- 4为例选择帧同步器参数和帧同步码组 ,实现了一种应用于高速SDH系统的并行帧同步器的设计。     

基于信任的普适计算服务选择模型

借鉴人类社会的行为规律,提出普适计算中信任关系的建立、信任度的衡量、以及基于信任的服务选择模型;并依据信任的滞后性和服务选择前瞻性矛盾的动态演化规律,通过多角度(直接、间接)评估、喜好偏差调整和信任更新等综合手段,构造一套较健全的信任评估体系,以提高服务选择模型的准确可靠性。     

User impersonation in key certification schemes

In this note we exhibit some weaknesses in two key certification schemes. We show how a legitimate user can impersonate any other user in an ElGamal-based certification scheme, even if hashing is applied first. Furthermore, we show how anybody can impersonate users of the modular square root key certification scheme, if no hashing occurs before the certification. This shows that it is essential for this certification scheme to hash a message before signing it.     

Iterative key frame selection in the rate-constraint environment

Video representation through key frames has been addressed frequently as an efficient way of preserving the whole temporal information of sequence with a considerably smaller amount of data. Such compact video representation is suitable for the purpose of video browsing in limited storage or transmission bandwidth environments. In this case, the controllability of the total key frame number (i.e. key frame rate) depending on the storage or bandwidth capacity is an important requirement for the key frame selection method. In this paper, we present a sequential key frame selection method when the number of key frames is given as a constraint. It first selects the pre-determined number of initial key frames and time-intervals. Then, it adjusts the positions of key frames and time-intervals by iteration, which reduces the distortion step by step. Experimental results demonstrate the improved performance of our algorithm over the existing approaches.     

云计算发展及关键技术探讨

云计算是互联网时代商业模式上的创新,被看作是信息产业的第三次革命。从客观的角度来分析,云计算融入了很多的技术,实现了相关领域的较大进步。但是,由于云计算的部分关键技术还没有得到彻底的健全,所以在运用上,还是表现出了一些非常小的瑕疵,这是需要日后重点解决的。云计算在发展过程中,促进了各行各业工作的进步,是今后需要重点研究的领域。     

Key frame extraction based on visual attention model

Key frame extraction is an important technique in video summarization, browsing, searching and understanding. In this paper, we propose a novel approach to extract the most attractive key frames by using a saliency-based visual attention model that bridges the gap between semantic interpretation of the video and low-level features. First, dynamic and static conspicuity maps are constructed based on motion, color and texture features. Then, by introducing suppression factor and motion priority schemes, the conspicuity maps are fused into a saliency map that includes only true attention regions to produce attention curve. Finally, after time-constraint cluster algorithm grouping frames with similar content, the frames with maximum saliency value are selected as key-frames. Experimental results demonstrate the effectiveness of our approach for video summarization by retrieving the meaningful key frames.     

Rate-driven key frame selection using temporal variation of visualcontent

A simple and fast method to select the assigned number of key frames in a video shot is presented. The algorithm selects the key frames so that the temporal variation of visual content within a video shot is equally distributed to each key frame. Simulation results on a real video sequence are shown to be in agreement with the human visual perception     

基于身份密钥交换的安全模型

研究了基于身份的密钥交换协议的可证明安全问题.在通用可组合安全框架下,提出了基于身份密钥交换协议的模型.在攻击模型中,添加了攻陷密钥生成中心的能力.根据基于身份密钥交换的特点,设计了基于身份密钥交换的理想函数.在新的攻击模型和理想函数下,提出的模型既保证了基于身份密钥交换的通用可组合安全性,又保证了一个重要的安全属性--密钥生成中心前向保密性.此外,带有密钥确认属性的Chen-Kudla协议可以安全实现基于身份密钥交换的理想函数.     

Performance Analysis Applications in Virtual of Interactive Desktop Machine Environment

To assess the feasibility of hosting interactive desktop applications in virtual machine environment, this paper measures and analyzes the interactive performance of the desktop operating system in Xen environment. The experimental results show that short-latency input events are not sensitive to the virtualization overhead but the average response latencies of long-latency events in Xen system are remarkably longer than the latencies in the unvirtualized system. In fact, the larger variance of response latency, instead of the longer latency itself, is the most important performance problem for the virtualized approach. Our analysis shows that the main reason of the poor performance is the insufficient CPU share of the driver-specific virtual machine, which causes the long freezing periods of other guest virtual machines. While the offline adjustment can alleviate the problem, an online adaptive adjustment of the CPU allocation is necessary for the practical use of Xen hosted desktop systems.     

浅析基于云计算的分布存储关键技术

随着网络技术的发展,云概念成为网络进步的主题。目前,我国将云计算作为新型的研究资源,利用云计算的约束,提高数据处理、存储的安全性。云计算在实际应用中,具有较高的服务价值,将其作为高技术的途径,应用于分布存储技术中,提高分布存储的性能,同时提升分布存储的高效性。因此,本文通过对云计算营造的环境进行分析,研究分布存储的关键技术。     

分布式多入多出正交频分复用系统帧同步的阈值选取准则

利用分布式多入多出正交频分复用（Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing,MIMOOFDM）系统中帧同步度量函数的统计特征和正确帧同步概率的理论计算方法,提出了理论上能达到100%正确帧同步的阈值选取准则,同时给出了基于正态分布的3σ原则简化准则.理论分析发现：阈值选取准则在高于指定的信噪比（Signal Noise Ratio,SNR）下可达到任意的正确帧同步性能设计要求;简化准则计算量非常小,且正确帧同步概率能达到99.87%;发射天线增加时帧同步度量减小,帧同步算法需要进行改进.通过仿真实验验证了系统在不同MIMO发射天线数目和指定SNR下阈值选取准则的准确性和有效性.     

网格关键技术论析

信息技术的下一个浪潮高峰是万维网(World Wide Web)升级为网格(Grid)。了解、认识。进而应用网格技术意义重大。网格的关键技术主要有网格硬件、网格操作系统、网格应用层面、网格计算以及其他一些关键技术。